Based on current trends, it is expected that minimum feature sizes in microelectronic devices will approach 0.5 .mu.m by the early 1990's. At present, it appears that photolithography, using near to mid UV radiation is limited to replication of structures with dimensions of about 0.6 .mu.m. E-beam and X-ray sensitive resists are at the forefront of the manufacture of integrated circuits because they permit the formation of smaller images than do resists which are responsive only to light radiation. The procedure is to expose the resists applied to suitable substrates to an electron beam or X-rays to generate features having submicron dimensions. After the resist is developed, the substrate not protected by the resist is etched, usually by a chemical or plasma etching.
One of the difficulties with such a procedure is the scarcity of useful negative-working resists. Not only must the resist demonstrate sensitivity to an X-ray or E-beam, but it must also resist deformation and dissolution by the etching process applied to the substrate or base material, usually a semiconductor. Thus, only a few resists have been found to be useful in providing features of submicron dimensions with strict tolerances. For example, superior E-beam and X-ray sensitive resists are described in U.S. Pat. Nos. 4,289,842 and 4,568,734. The '842 patent describes novel acrylate copolymer materials with enhanced sensitivity and plasma etch resistance. The '734 patent describes a resist comprising copolymers of either allyl or propargyl methacrylate and an acrylate or methacrylate bearing an oxygen-containing heterocyclic ring. Although such resists have been particularly useful, there is a need for radiation-sensitive resists which are compatible with present and future X-ray sources, target materials, imaging techniques and which stand up to high energy image transfer processes such as plasma etching.
Therefore, what has been desired is a negative-working resist material having excellent sensitivity, good plasma etch resistance, submicron resolution capability, and which is adaptable to a variety of imaging techniques.